feat(commands): central command registry, command palette & shortcuts cheat-sheet (#721)

[svenmalvik]

What & why

First deliverable for #721 (an epic). Introduces a single source of truth for command → keybinding consumed by both the native menu and the renderer, replacing today's three-places-per-shortcut wiring (menu accelerator + preload whitelist + ad-hoc keydown/on() handler). Adds the two discoverability surfaces the issue asks for: a command palette and a shortcuts cheat-sheet.

Design spec: docs/superpowers/specs/2026-06-14-keyboard-command-registry-design.md (committed here).

Approach

src/shared/commands/catalog.ts is pure data (id, title, category, accelerator, menu placement), importable by main, renderer and tests.

• Main (app-menu.ts) generates every accelerator menu item from the catalog; each click fires one unified command:run IPC.
• Renderer (useCommands) dispatches command:run through a tested id → handler map wired to functions that already exist in App.tsx (no new feature logic). The palette calls the same runCommand. Unknown ids no-op with a warning.
• No renderer global-keydown dispatcher — native menu accelerators already work reliably over the embedded xterm/Monaco. Lowest-risk path.

What you get

• ⇧⌘P command palette (fuzzy) — distinct from ⌘P file Quick Open.
• ⇧⌘/ shortcuts cheat-sheet overlay + a read-only Settings → Shortcuts tab.
• Existing bindings migrated onto the catalog (Settings, Find in Files, panel toggles, favorites, Quick Open) — behavior unchanged.
• New commands (reusing existing functions): new / next / previous / delete agent, commit, create PR, focus chat / terminal / file-tree, toggle theme.

De-confliction

Keys avoid Electron roles (⌘R, ⇧⌘R, ⌃⌘F, zoom, ⌘W/M/H/Q), Monaco bindings (⌘/, ⇧⌘O, ⌃G) and existing app bindings. The issue suggested ⌘/ for the cheat-sheet; this uses ⇧⌘/ because a native ⌘/ accelerator would globally steal Monaco's comment-toggle.

Deferred to follow-ups (per spec)

Editor tab next/prev/close (⌘W collision), rename/interrupt agent (no existing renderer fn), switch repo/workspace by key, and user-customizable keybindings (the Settings tab is read-only for now).

Testing

• TDD on the pure units: accelerator-label, agent-cycle, catalog invariants (unique ids, no duplicate accelerators), command-handlers (every id has a handler; routing), CommandPalette (filter/Enter/Escape), and extended app-menu.test.ts (every catalog accelerator present; clicks send command:run).
• npm run typecheck:web clean; typecheck:node unchanged from baseline (only the pre-existing provisioning error remains).
• Full renderer + main/app suites: 797 passing. (4 editor suites fail to load locally on the pdf.worker?url symlinked-node_modules artifact — green on CI.)
• docs/architecture/app.md + preload.md updated for the catalog-driven menu; wiki-lint structural checks PASS.

Closes #721 partially (foundation); follow-up PRs land per-feature coverage and customization.

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